The MoFe protein and the Fe protein, which together constitute nitrogenase, are being characterized for their physical chemical and enzymatic properties. UV spectra and EPR spectra are being used to follow the pathway of electron transport in N2 fixation. Binding of ATP and its influence on the OR potential of the Fe protein as well as substrate binding to nitrogenase constituents are being investigated. Nitrogenases from Rhodospirillum rubrum and Bacillus polymyxa are being purified so that they can be compared with nitrogenases from Clostridium pasteurianum. The nature of the enzymatic reaction catalyzed by purified hydrogenase is under study. The role of blue-green algae in the eutrophication of freshwater lakes is being assessed. Work is being completed on establishing the OR potentials of a variety of ferredoxins.